1. Field of the Invention
This invention relates to a magnetic reading and writing device and a controller of the device.
2. Description of the Related Art
In current hard disk drives, in order to raise recording densities to the extent possible and realize large recording capacities for specific combinations of magnetic reading and writing heads and a magnetic recording medium, processing has been performed to optimize the recording current and track density, as well as the heater power for control of the flying height of the magnetic reading and writing heads. Optimum conditions differ depending on the radius, due to the circumferential speed dependence and skew dependence of the head flying characteristics, as well as the radial dependence of the magnetic characteristics of the magnetic recording medium. Hence, in general, optimization processing depending on the radius has been performed in a magnetic recording system. Specifically, the write current, distance between tracks (hereafter called the “track pitch”), linear recording density, as well as the heater power for the flying height control are selected so as to maximize the recording density at each radius, as a result of which drive storage capacity is optimized.
Japanese Patent Application Laid-open No. H8-45007 discloses a magnetic disk device which performs correction of writing signals and reproduced waveforms is disclosed. In the magnetic disk device, when data is received from a higher-level device during operation, a recording system converts the data into recording signals and outputs the signals to the magnetic head, thereby recording the recording signals on the magnetic disk. At this time, a preshifter performs correction such as delaying the recording signals. The correction amount in this case is calculated by recording correction amount calculation means based on the peak position of a reproduced waveform. On the other hand, a reading system of the device converts readout waveforms read by the magnetic head from the magnetic disk into data, and outputs the data to a higher-level device. At this time, the filter corrects the amplitude and similar of the readout waveforms. The correction amount in this case is calculated by read/write correction amount calculation means, based on the pulse width of the readout waveforms (see paragraphs [0008] and [0009] of Japanese Patent Application Laid-open No. H8-45007). In accordance with this device, by calculating a correction amount in advance for each track, the correction amount which absorbs scattering at the time of magnetic disk manufacture and the like can be calculated (see paragraphs [0021], [0026] and [0027], and similar of Japanese Patent Application Laid-open No. H8-45007).
Further, Japanese Patent Application Laid-open No. 2009-129532 discloses a mechanism which, in order to compensate readout signal output, uses a heater for control of the flying height of a magnetic read/write head.
In an actual magnetic recording medium, there are cases in which there is a gentle characteristic distribution not only in the radial direction, but in the circumferential direction as well. If reading and writing optimization processing is performed using such a magnetic recording medium with a dependence only on the radial direction, as in the prior art, then it is possible that the recording capacity will be greatly inferior to what should in principle be obtained when performing optimization which includes a dependence on the circumferential position as well. In particular, where the write performance is concerned, when there is unevenness in the circumferential position, under constant conditions in the circumferential position, the write width is broad in portions where the write performance is high and the track pitch cannot be narrowed. Conversely, in portions where the write performance is low, under conditions optimized for portions with high write performance, there is the concern that write performance will be inadequate.